CFM Calculations
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Originally Posted by JETPILOT
When calculating engine CFM should I figure CFM @ the point I want to make maximum power (6250RPM)? Or @ redline 660RPM?
Thanks
JET
Thanks
JET
cid*rpm*0.5*E(v) / 1728
Saw your other post requesting comp. maps. Are you looking to upgrade turbo's?
#3
I'm no one to disagree with you, but peak torque? Can that be right? Peak torque is like 4200 rpm if I remember correctly. The engine will be run up to 6250rpm so after 4200 the turbo will be out of it's effieciency range. Yes... I am looking for a replacment turbo for my single turbo kit.
JET
JET
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You should be looking at CFM for the entire operating range not just peak pressure. That formula is correct for CFM just make sure to convert to lb/min as most compressor charts read in lb/min. What you are basically looking for is the peak air flow you require the turbo to produce (although its a VERY rough estimate each 1 lb/min of compressor air flow can be translated to 10 WHP). Using a rough calculation (see prior note) if you want to make 450 RWHP you want to look at what efficiency the compressor is for 45 lb/min at the pressure ratio you plan to run. Not to talk **** at all but have you read the book Maximum Boost by Corkey Bell? It would help you better understand what to look for in a turbo (compressor and turbine that is).
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You need something bigger than a gt35r if you want it to pull to redline, and like a .96 exhaust housing. www.majesticturbo.com call these guys and ask them what size turbo they would recomend. I came up with a gt35r to make over 500 hp at the wheels...
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Originally Posted by rocks
You need something bigger than a gt35r if you want it to pull to redline, and like a .96 exhaust housing. www.majesticturbo.com call these guys and ask them what size turbo they would recomend. I came up with a gt35r to make over 500 hp at the wheels...
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Originally Posted by JETPILOT
I'm no one to disagree with you, but peak torque? Can that be right? Peak torque is like 4200 rpm if I remember correctly. The engine will be run up to 6250rpm so after 4200 the turbo will be out of it's effieciency range. Yes... I am looking for a replacment turbo for my single turbo kit.
JET
JET
Now if you're looking to play around with plots on the turbo comp map to see how efficient the turbo will be I'd calculate RPM at the point you think it'll hit full boost. Then calculate in the RPM just shy of redline and you should have 2points from which to draw your line through the map.
Don't know if you already know the formula but I'll post it:
Pressure Ratio = 14.7 + boost / 14.7
Basic Engine CFM = (formula above in previous post)
Airflow Rate = Pressure Ratio * Basic Engine CFM
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Originally Posted by atlsupdawg#2
Sorry JET I was thinking more along the lines of the engines peak volumetric efficiency which is usually at peak torque.
Now if you're looking to play around with plots on the turbo comp map to see how efficient the turbo will be I'd calculate RPM at the point you think it'll hit full boost. Then calculate in the RPM just shy of redline and you should have 2points from which to draw your line through the map.
Don't know if you already know the formula but I'll post it:
Pressure Ratio = 14.7 + boost / 14.7
Basic Engine CFM = (formula above in previous post)
Airflow Rate = Pressure Ratio * Basic Engine CFM
Now if you're looking to play around with plots on the turbo comp map to see how efficient the turbo will be I'd calculate RPM at the point you think it'll hit full boost. Then calculate in the RPM just shy of redline and you should have 2points from which to draw your line through the map.
Don't know if you already know the formula but I'll post it:
Pressure Ratio = 14.7 + boost / 14.7
Basic Engine CFM = (formula above in previous post)
Airflow Rate = Pressure Ratio * Basic Engine CFM
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Mia thats why i said bigger than a gt35r. I know for sure a holset HX40 would make that power and pull to redline. It wouldnt be that laggy either, full boost would be around 3500-3700 rpms. You can make over 600hp on a 2.3L ford turbo with a holset hx35w, and the 40 is alot bigger than it. The calculation i did for a gt35r would maybe do 500-550 pushing. If you want a turbo that wouldnt peter out get a damn holset HX40.
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Originally Posted by JETPILOT
Well if you read the book all i have to do is ask you!
My lb/min calculations are 33.7 lbs/min @ 15psi @ 6600rpm with a preesure ratio of 2.0
Sound about right?
JET
My lb/min calculations are 33.7 lbs/min @ 15psi @ 6600rpm with a preesure ratio of 2.0
Sound about right?
JET
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Originally Posted by MIAPLAYA
All good data except you still need to plot airflow and pressure ratio before boost threshold is reached. You have to factor in the surge line at some point to ensure you are using a compressor that will stay in front of it throughout the operating range...
I definitely agree but wouldn't this be more of an issue if you started playing around with different A/R's and turbine wheel trims??
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Originally Posted by rocks
Mia thats why i said bigger than a gt35r. I know for sure a holset HX40 would make that power and pull to redline. It wouldnt be that laggy either, full boost would be around 3500-3700 rpms. You can make over 600hp on a 2.3L ford turbo with a holset hx35w, and the 40 is alot bigger than it. The calculation i did for a gt35r would maybe do 500-550 pushing. If you want a turbo that wouldnt peter out get a damn holset HX40.
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Originally Posted by atlsupdawg#2
MIA,
I definitely agree but wouldn't this be more of an issue if you started playing around with different A/R's and turbine wheel trims??
I definitely agree but wouldn't this be more of an issue if you started playing around with different A/R's and turbine wheel trims??
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Mia holset has that its called Map Width Enhancement.It recirculates air at lower rpms to prevent surging, at high rpms it pulls more air into the back set of blades. this helps the turbo flow about 10-15% more air and prevents surging, im used to holsets on gas engines. They also use titanium wheels.... They will not surge if you use a proper size waste gate. These turbos also designed to spin backwards since diesels do not use a blow off valve, or bypass valve..
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Originally Posted by JETPILOT
Well if you read the book all i have to do is ask you!
My lb/min calculations are 33.7 lbs/min @ 15psi @ 6600rpm with a preesure ratio of 2.0
Sound about right?
JET
My lb/min calculations are 33.7 lbs/min @ 15psi @ 6600rpm with a preesure ratio of 2.0
Sound about right?
JET
213.5 * 6600 * 0.5 * .87 / 1728
Guestimated on the E(v) at 87%
According to the map you posted that'll put you on the 79% efficiency island...
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Originally Posted by rocks
Mia holset has that its called Map Width Enhancement.It recirculates air at lower rpms to prevent surging, at high rpms it pulls more air into the back set of blades. this helps the turbo flow about 10-15% more air and prevents surging, im used to holsets on gas engines. They also use titanium wheels.... They will not surge if you use a proper size waste gate. These turbos also designed to spin backwards since diesels do not use a blow off valve, or bypass valve..
#20
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Originally Posted by atlsupdawg#2
Sounds about right. I came up with 35.5 lbs/min (3.5 PR)
213.5 * 6600 * 0.5 * .87 / 1728
Guestimated on the E(v) at 87%
According to the map you posted that'll put you on the 79% efficiency island...
213.5 * 6600 * 0.5 * .87 / 1728
Guestimated on the E(v) at 87%
According to the map you posted that'll put you on the 79% efficiency island...